The present invention relates generally to a plastic closure for use with an associated container, and more particularly to a linerless closure including a flexible sealing flap and an annular pressure bead or wall which cooperates to seal the sealing flap against a container finish.
Molded plastic closures for containers have become increasingly popular for closing and sealing the contents of containers, such as for use with carbonated and non-carbonated beverages, condiments, and other food products, as well as for use on non-food products, such as motor oil. While various plastic closure constructions have been known for a number of years, special design considerations must be made in order for the desired sealing to be effective, and to facilitate high-speed manufacture and application of such closures.
In order to achieve the desired sealing performance, a number of heretofore known closure constructions have been of a composite nature, including a relatively rigid outer plastic shell, and a relatively pliable and soft inner sealing liner. Such lined closures, formed, for example, in accordance with commonly-assigned U.S. Pat. No. 4,343,754, U.S. Pat. No. 4,378,893, U.S. Pat. No. 4,407,422, and U.S. Pat. No. 4,497,795, have proven to be effective for use on containers, including containers having carbonated or otherwise pressurized contents. The desired sealing performance is achieved by configuring the closure construction to include a relatively rigid and strong, threaded outer closure cap, with an in situ formed liner positioned against an end wall portion of the cap. Closures in accordance with these patents are configured to form a so-called top/side seal, in that the liner can sealingly engage both a generally upwardly facing surface of an associated container, as well as a generally outwardly facing, side surface of the container.
Linerless closures on the other hand offer the advantage of simplifying manufacturing and reducing material costs compared to lined closures. However, the heretofore known linerless closures have not provided a seal as effective as lined closures. In a linerless closure, the sealing surface is molded from the same material as the other features of the closure. The elastic property necessary to accomplish a highly effective seal is compromised by the design requirements of other features of the closure cap, such as the structural requirements for tamper evidence features and threads. Selecting a material for the closure is therefore a balancing act, particularly when the container contents are pressurized.
Linerless closures are disclosed for example in U.S. Pat. Nos. 5,259,522; 4,540,102; 4,061,240; 5,782,369; 5,609,263; 4,196,818; 3,203,571; 4,276,989; 4,598,835; and 4,450,973.
The ability to achieve a long lasting seal and the ability to maintain the long lasting seal during adverse conditions is very important. Such adverse conditions include xe2x80x9cdomingxe2x80x9d (i.e., material creep of the closure end wall, causing the end wall to dome outwardly) and xe2x80x9crelaxingxe2x80x9d (i.e., top loading of stacked bottles in a warehouse).
The present inventor has recognized that it would be desirable to provide an improved linerless closure which maintained an effective long lasting seal that remains effective during adverse conditions.
The present invention provides a linerless closure with an improved, long lasting seal. The closure includes a shell having an end wall and a depending sidewall or skirt. Within the shell, a side seal protrusion or sealing flap extends radially inwardly from the sidewall. A vertical protrusion extends axially from the end wall of the shell. A radially resilient structure is formed between the vertical protrusion and the sidewall of the shell, at the end wall.
When the closure shell is fit and tightened onto a container finish, such as onto a bottle neck, the flap is deflected by the bottle finish to bend against the vertical protrusion. The flap is sufficiently long to seal against a side region of the container finish, around the container finish radius, and to the top surface of the container finish. The top surface of the container finish axially presses the flap to the end wall of the closure shell, and the side of the container finish radially presses the flap against the vertical protrusion. The flap has one or more bends to allow the flap to better conform to the various sealing surfaces.
The flap is clamped between the side of the container finish and the vertical protrusion. The radially resilient structure can be a lattice-like gusset structure, and is configured to act as a plurality of springs which resiliently urge the vertical protrusion against the flap and the flap against the side of the container finish. Even if the closure end wall domes or relaxes, the spring action of the gusset structure will maintain the radial force needed to keep the flap sealed between the side of the container finish and the vertical protrusion.
In accordance with the invention, other resilient structures can be used instead of the lattice-like gusset structure. A sufficiently resilient solid annular member, for example, could be used to radially, resiliently urge the vertical protrusion against the flap.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.